Various methods have been used to determine mechanical properties of elastic type materials. One of these methods employs a piezoelectric transducer connected to one end of an elongate test specimen with a needle lightly touching the surface of the elongate test specimen at some known distances from the transducer (vibration) input to measure amplitude and phase difference over that known distance. From the loss in amplitude and phase difference from the input to the output, the characteristics of the material can be determined. One approach, discussed in the article "Propagation of Audiofrequency Sound in High Polymers," by R. S. White, B. A. Mrowca and E. Guth, appears in the Journal of Applied Physics, Vol. 20; No. 6, pages 481-485 (June 1949). Another approach is discussed by the inventors in "Automated Dynamic Young's Modulus and Loss Factor Measurement," Journal, Acoustics Society of America, Vol. 66; No. 2, August 1979. This last article describes an advanced progressive wave initiating apparatus used in conjunction with an automated data processor. A phonograph cartridge is positioned on the surface of a test strip at selected distances from an electromagnetic shaker input. The length of the test strip must be sufficient to defeat the creation of a standing wave between the strip ends. Relative attenuation and phase shift are measured for each selected needle distance. Since the input frequency is known, propagation velocity in that particular material can be determined. The apparatus and method according to this approach is disclosed and claimed in our co-pending U.S. patent application entitled "Instrument for Measuring Dynamic Viscoelastic Properties" Ser. No. 172,585, filed July 28, 1980, now U.S. Pat. No. 4,352,292.